Briarwood is the "hospital" Jaenelle Angelline was sent to off and on from the time she was 5 until she was 12. Briarwood, located in Chaillot in Terreille is in reality a place where the men working there (referred to as the uncles) force the young girls into sexual acts and rape usually breaking them on their Virgin Night and often killing them.
"Briarwood is pretty poison. There is no cure for Briarwood." - Jaenelle Angelline
When Greer raped Jaenelle and her blood was spilled it triggered a web Jaenelle had woven. The spell caused all the uncles of Briarwood suffer from what they had done to all the girls in the facility. Every one of them got back what they had inflicted - for example one man felt that his arms were being ripped off even though nothing was really happening. The cause of this was that he had ripped off a girl's arm when she had hit him.